Photographic silver-halide emulsions containing trinuclear cyanine dyes



March 7, 1950 A w. ANISH ETAL 2,500,112

PHOTOGRAPI-iIC SILVER-HALIDE EMULSIONS CONTAINING TRINUCLEAR CYANINE DYES Original Filed Aug. 15, 1946 a Shets-Sheet 1 T 2 5 N-N II II v/ C=CHCH=N.C CCH=CHCH=C N s W FIG. 1

FIG.2

ALFRED W. ANISH CHARLES A. CLARK INVENTORS arD' ATTORNEYS March 7, 1950 A. w. ANISH ETAL 2,500, 1

PHOTOGRAPHIC SILVER-HALIDE EMULSIONS CONTAINING 'I'RINUCLEAR CYAN'I'NE DYES Original Filed Aug. 15, 1946 3 Shets-SheetZ 2 5 N a H N \S "H- 2% 2% I" FIG. 3

fa s s W. E? =NC\S,C"-CH= "H 'H 2 5 2 5 1- 340 400 460 520 580 640 700 760 FIG. 4

ALFRED W. ANISH CHARLES A. CLARK INVENTOR ATTORNEYS March 7, 1950 A. w. ANISH ETAL 2,500,112

PHOTOGRAPHIC SILVER-HALIDE EMULSIONS CONTAINING TRINUCLEAR CYAN'INE DYES Original Filed Aug. 15, 1946 3 Sheets-Sheet 3 H C CH I H C CH I l C2H5 v 2 5 clo' FIG. 6

ALFRED VV. ANISH CHARLES A. CLARK INVENTOR ATTORNEYS Patented Mar. 7, 1950 PHOTOGRAPHIC SILVER-HALIDE EMUL- SIONS CONTAINING TRINUCLEAR CYA- NINE DYES Alfred W. Anlsh, Vestal, and Charles A. Clark,

Binghamton, N. Y., assignors to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware Original application August 15, 1946, Serial No.

690,832, now Patent No. 2,476,525, dated July 19, 1949. Divided and this application September 25, 1946, Serial No. 699.338

4 Claims. 1

This invention relates to photographic gelatino silver-halide emulsions, and more particularly to photographic light-sensitive silver-halide emulsions containing dyes of the trinuclear cyanine type.

Cyanine dyes containing more than two nuclei are already known. Dyes of this category are illustrated, for example, in U. S. Patent 2,155,475, and in French Patent 832,352. It will be noted that in the dyes referred to in the United States patent the nucleus appearing in the dye, in addition to the two terminal nitrogenous heterocyclic nuclei, is aromatic in character. On the other hand, in certain of the dyes of the French potent, the meso nucleus is heterocyclic and of the type known as rhodanine nucleus. In both types of dyes, however, the meso nucleus serves to interrupt the methenyl chain by which the terminal heterocyclic nitrogenous nuclei are linked toether.

Rhodacyanine dye salts, which contain in the polyrnethine chain a rhodanine' ring, are also known. These dye salts are prepared by first alkylating a suitable merocyanine and then condensing the alkylated product with a cyclammonium quaternary salt. In this condensation reaction, the alkylmercapto group of the alkylated merocyanine condenses with the methyl group attached in a-position to the nitrogen atom, of a cyclammonium quaternary salt to give the desired dye salt.

Trimethine dyestuffs containing an oxadiazole, substituted by a, furan ring, are also known. It is also known that cyanine dye condensations may be carried out through an active amino group of a cyclammonium base or salt to yield dyes of the azamethine type. The simultaneous condensation, however, of both an amino and a methyl group of an oxadiazole or thiadiazole compound with a cyclammonium dye salt to yield trinuclear cyanine dyes has not been previously suggested or described.

We have now discovered a new class of trinuclear cyanine dye salts in which the central nucleus, diazole or triazole, is linked to the other two nuclei by both a methine and an azamethine chain. These new dye salts have properties which are not possessed by the known trinuclear dye salts. For instance, the dyes are not only excellent sensitizers for both orthochromatic and panchromatic fllm emulsions, but are also excellent sensitizers for color film, being unaffected by the presence of color components, and exhibiting the property of non-migration from the layer in which they are incorporated. Moreover, we have found that these new dyes have appreciable water solubility and are readily removed from the exposed emulsion layer during processing.

An object of the present invention is to provide photographic silver-halide emulsions with trinuclear cyanine dyes containing a diazole or triazole nucleus.

A further object is to provide such dyes which are added to photographic silver-halide emulsions or coated thereon as an over-coating, whereby the sensitivity of the emulsion is increased.

A still further object is to provide photo-sensitizing dyestufis having appreciable water solubility and readily removed from the exposed emulsion layer during processing.

Other objects and advantages of this invention will become apparent. by reference to the following specification in which its preferred details and embodiments are described.

This invention is predicated upon our discovery that 1 mol of a 3,4-diaz0le or 1.3,4-triazole salt, containing an amino group in 2-position and a methyl group in S-position with the nitrogen atom in 4-position substituted by an alkyl or aralkyl group, can be condensed with 2 mols of a nitrogenous heterocyclic dye salt of the type used in cyanine dyes. This discovery is wholly unexpected and surprising, since 3,4-diazole and 1,3,4-triazole salts, with the N atom in 3- or 4-position substituted by an alkyl or aralkyl group and containing methyl groups in the 2- and 5-positions are only reactive through one of these groups, 1. e., through the methyl group in the 2- or 5-position, but not through both groups. Similarly, 3,4-diaz0le or 1,3,4-triazole salts containing an amino group in 2-position and a methyl group in 5-po'sition, and wherein the nitrogen atom in 3-position is substituted by an alkyl or aralkyl group, are reactive only through the .amino group.

The trinuclear cyanine dyes prepared according to the present invention are characterized by the following general formula:

wherein A represents the atoms necessary to complete a nitrogenous heterocyciic system of the type used in the preparation of cyanine dyes, such as, for example, oxazole, oxazoline, thiazole, thiazoline, seienazole, seienazoline, benzothiazole, benzoselenazole, benzoxazole, naphthothiazole, naphthosoienazole, indolenine, pyridine and its polycyclic homologues such as quinoline and napthoquinoline, and the like. The polycyclic compounds of these series may also be substituted in the carbocyclic rings with one or more groups, such as alkyl, as below, aryi, i. e., phenyl, etc., amino, hydroxy, alkoxy, e. g., methoxy, ethoxy, propoxy, etc., and methyienedioxy groups. R is a hydrocarbon group, for example, alkyl group, e. g., methyl, ethyl, propyl, butyl, amyl, and the like, or araikyl group, e. g., benzyl, phenylethyl, and the like, X represents an anionic acid radical, e. g., Cl, Br, I, C104, SOlCHn, SO4C2H5, SOaCeH4CH3, and the like, Y represents either oxygen, sulfur, or NR1, wherein R1 is either hydrogen or an alkyl of the same value as R, m represents 0, 1, or 2, and p represents or 1.

The process of preparing the above trinculear cyanine dyes comprises condensing, at room temperature or by heating as on a steam bath or under reflux conditions, 1 mol of a cyclammonium quaternary salt of 2-amino-5-methyl- 3,4-diazole, or 1,3,4-triazole with 2 mois of a cyclammonium quaternary cyanine dye intermediate, of the type used in the preparation of cyanine dyes, in the presence of an acid binding agent such as a nitrogenous heterocyclic base containing a small quantity of a tertiary base which may include a small quantity of acetic acid or acetic anhydride.

The anions of the dye salts thus obtained are readily converted into different anions by methods well-known in the art.

The cyclammonium quarternary salts of 2- amino-5-methy1-3,4-diazoies and 1,3,4-triazoles utilized in the condensation reaction are characterized by the following general formula:

wherein R, X and Y have the same values as above, and are obtained by quaternizing any one of th following diazoles as will be pointed out hereinafter.

J. Prakt. Chem. 122, p. 289-318, 1929 2-amino-5-methyl-1,3,4-triazole The quaternary salt of Z-amino-S-methyl- 1,3,4-triazole is prepared by heating, under pressure, the triazole with an alkyiating agent, such as, methyl or ethyl iodide, sulfate, methyl-ptoluenesulfonate and the like.

The cyclammonium salts of the type used or proposed for the production of cyanine dyes, and utilized in accordance with the present invention, are represented by the following general formula:

(CH-CH wherein A, R, m, p, and K have the same values as above, and R2 represents an anilido radical, i. e., anilido, acetanilido or 4-chloroacetanilido, and hydrocarbon mercapto groups, e. g., methylmercapto, ethylmercapto, propylmercapto, phenylmercapto, naphthyimercapto, and the like, R; being anilido only when m is 1 or 2.

As examples of represenative cyclammonium quaternary cyanine dye salt intermediates falling within the above configuration the following may be mentioned:

benzothiazolium benzoselenazolium The above cyclammonium quaternary cyanine dye salt intermediates are well-known to the art, and hence the methods for their preparation need not be discussed herein. While the above dye intermediates are disclosed as being in the form of the preferred ethiodides, it is to be understood that they may also be employed in the form of the other quaternary salts previously mentioned.

As acid binding agents employed for the prep-- aration of the dyes of the present invention, the

following may be advantageously employed: P idine, methylpyrldine, dimethylpyridine, ethylpyridine, ethylmethylpyridine, trimethylpyridine, quinoline, and the like, containing a tertiary aliphatic base such as triethylamine, triprcpylamine, tributylamine, etc., as a catalyst. The tertiary base may also include, if so desired, a small quantity of acetic acid or acetic anhydride. In general, the amount of condensing (acid binding) agent used may vary within wide limits, e. 3., from i to 25 mois. Concentrations ranging from 1 mol to about 15 mois are preferred.

In the preparation of these new trincuiear cyanine dyes, the 2-amino-5-methyl-3,4-diazole and 2-amino-5-methyl-1,3,4-triazole bases are converted into their corresponding alkyl or aralkyl quaternary salts by heating the base with an alkyl or araikyl halide, usually employed in such a reaction, in a bomb or sealed tube at a tempera- 2-amino-3-ethyl-5-methyl 1,3,4-thiadiazoiium ture ranging from 100 to 120 C. for 3 to 6 hours. iodide, and is incapable of undergoing a con- The quaternization of the diazole base must densation reaction through both the amino and be carefully controlled, otherwise an undesirable methyl groups. It did, however, undergo a conquantity of the isomeric form of the quaternary densation reaction through the amino group only. salt is obtained. It is believed that the reactive form, leading to the trinuclear cyanine dyes Examplgnn of the present invention, has the following configuration N-N n rim- 8-011 I N--N o g g 2-amlno-4-ethyl-5-methyl-1,3,4-oxadiazolinium iodide Example I was repeated with the exception that an equivalent quantity of 2-amino-5- AS a by-p (isomeric form) 01 this methyl-1,3,4-oxadiazole was substituted for 2- action, a secondary quaternary salt is isolated, m q s m m m which probably has the following configuration:

R Example III 1't 2o F' u g x- N-N H|N C OH; A g

\ Hm- 431-1, I-

Y This by-product is not useful in the prepara- (5 tion of the dyes of the present invention, since it undergoes dye condensations only through the 1,4-diethyl-2-amin0-5-metl1yl-1,3,4-triazolium iodide amino group. Example I was repeated with the exception The following examples describe, in detail, the that an equivalent quantity of 1-ethy1-2-amlnomethod for preparing the quaternated diazoles 5-methyl-l,3,4-triazole was substituted for 2- and triazoles, and the trinuclear cyanine dyes amino-5-methyl-1,3,4-thiadiazole. therefrom but it is to be understood that they While the above diazolinium salts have been are presented merely for the purpose of illustration and are not to be construed as limitative. r ig gz g ggs ggg hg gfi g fifig g j i fig si. 3 Example I pared in the form containing other anionic acid radicals. For example, instead of employing ethyl iodide as the quaternating agent, methyl,

ethyl, or propyl chloride, bromide, dimethyl sulmN-d L-CH: fate, benzyl bromide, methyl p-toluene-sulfonate,

and the like may also be employed. The preparation of the trinuclear cyanine dyes, 2 ammo 4 ethyl 5 methyl tmadmouum iodide while utilizing the diazolinium salts as above pre- A mixture of 6 grams of 2-amino-5-methylpared, is illustrated by the following examples.

Example IV CIHI s N l v s O=OH-OH=N- OH=OHOH=O I- s 61H: BrHl 1,3,4-thiadiazole and 15 grams of ethyl iodide was One gram of 2-amino-4-ethyl-5-methyl-1,3,4- heated in a sealed bomb, the'temperature being thiadiazolium iodide and 2 grams of 2-(5 carefully controlled in the range of 105-110 C., acetanilidovinyl) -3-ethyl-benz0thiazolium iodide for 4 hours. Upon cooling, the product was filwere dissolved in 20 cc. of pyridine and 2 cc. of tered and the residue extracted with several 2 cc. triethylamine added. The mixture was heated portions of anhydrous acetone until about 20 cc. to reflux for 5 minutes, cooled, and diluted with had been consumed. The acetone extract was several volumes of water. The green crystals precipitated with anhydrous ethyl ether and which separated out were filtered off and redried. The dried product is useful in preparing crystallized from ethyl alcohol. The dye sensithe trinuclear cyanine dyes of the present intized a silv'er-bromoiodide emulsion to 720 my vention, since the condensation reaction is siwith a maximum at 680 m Example V IHl (5311's multaneously brought about through the two One gram of 2-amino-4-ethyl-5-methyl-1,3,4- reactive groups, namely amino and methyl thiadiazolium iodide and 2.0 grams of 2-(pacegroups. tanilidovinyD-3-ethyl benzothiazolium iodide The acetone insoluble portion is thought to be were dissolved in 20 cc. of pyridine and 2 cc. of

triethylamine added. The mixture was heated over steam at 50 C., for 30 minutes, cooled, and diluted with about 60 cc. of water. The leafy crystals which separated out were filtered, and recrystallized from ethyl alcohol. The dye crystals were dissolved in methanol and precipitated as the perchlorate dye salt and purified by several crystallizations from methyl alcohol. The dye sensitized a silver-bromoiodide emulsion to 670 m l, with a maximum at 620 m l.

Example VI Six grams of 2 methylmercapto 1 ethyl G-methyl quinolinium iodide and 2 grams of 2 amino 4 ethyl 5 methyl 1,3,4 thia diazolium iodide were dissolved in 80 cc. of pyridine and 1 cc. of triethylamine added. The mixture was heated over steam for 1 hour, cooled, and diluted with water. The crystals which separated out were filtered off and recrystallized from n-butanol. The dye sensitized a silverbromoiodide emulsion to 610 m l, with a maximum at 560 my.

Example VII Two grams of 2-amino-4-ethyl-5-methyl-1,3,4- thiadiazolium iodide and 8 grams of 2-(fi-acetanilidovinyl) -3-ethyl-5,6-methylene-dioxy benzo- OHsO- thiazolium were dissolved in 60 cc. of pyridine and 2 cc. of triethylamine added. The mixture was heated under reflux for 3-5 minutes, cooled, and diluted with water. The crystals which separated out were filtered oil and recrystallized from methanol. The dye sensitized a silverbromoiodide emulsion to 740 m l, with a maxi- 0 and diluted with 2 volumes oi. water.

mum at 700 m Example VIII Five ,grams of 2-(p-anilidovinyl) -3-ethyl-4,5- diphenyl thiazolium iodide and 1.4 grams of 2 amino 4 ethyl 5 methyl 1,3,4 thiadiazolium iodide were dissolved in 50 cc. of pyridine containing 2 cc. 0! triethylamine and 1 cc. oi acetic anhydride. The mixture was heated under reflux for 5 minutes. cooled, and diluted with water. The crystals which separated out were filtered oil and recrystallized from ethyl alcohol. The recrystallized product was dissolved in methanol and precipitated as the perchlorate dye salt. The dye sensitized a silver-bromoiodide emulsion to 685 m, with a maximum at 635 mu.

Example IX One gram of 2-methylmercapto-3-ethyl-benzoselenazolium iodide and 0.3 gram of 2-amino-4- ethyl-5-methyl-1,3,4-thiadlazolium iodide were dissolved in 10 cc. of pyridine containing 1 cc, of triethylamine. The mixture was heated over an open fiame to drive oi! the mercaptan by-product. The reaction mixture was diluted with water, and the dye which precipitated was filtered oi! and converted to the bromide salt. The dye was purified and crystallized from ethyl alcohol. The

dye sensitized a silver-bromoiodide emulsion to 520 me, with a maximum at 480 m Six grams of 2-methylmercapto-3-ethyl-5,6- dimethoxy benzoselenazolium p-toluenesulionate and 2,7 grams of 2-amino-4-ethyl-5-methyl-1,3,4- thiadiazolium iodide were dissolved in 50 cc. of pyridine and 2 cc. of triethylamine. The mixture was heated over steam for 1 hour, cooled, The yellow crystals which separated out were filtered oil and recrystallized from methanol after conversion to the bromide salt. The dye sensitized a silverbromoiodide emulsion to 530 m with a maximum at 480 m 9 Example XI (IJSHI Oil-J N-N s-o-O K O=N Ji ZLOK=Q l1 M v N. 1 47H: H:

The crystals which separated out were dissolved in methanol and the dye converted to the perchlo- -Oom One gram of 2 methylmercapto 3 methyl 10 rate salt, and then purified by recrystallizing from 4(p) -tolyl-5-phenyl thiazolium iodide and 0.2 gram of 2-amin0-4-ethyl-5-methyl-1,3,4-t11iadiazolium iodide were dissolved in cc. of pyridine methanol. The dye sensitized a silver-bromoiodide emulsion to 730 m with a maximum at 690 my.

and 1 cc. of triethylamine added. The mixture Example XIV s I a N-N C=OHCH=N- /gOH=CHOH=O 41211: I (E111! was heated under refiux until the methyl mer- One gram of 2-(fi-acetanilidovinyl)-3-ethyl- D an' y-Dmduct was dissipated. After cooling benzoselenazolium iodide and 0.25 gram of 2- and diluting with water, the reaction mixture am1no 4 ethy1 5 methy1 L3,4 tmadmzouum was filtered and the Orange crystals recrysPaulzed dide were dissolved in 25 cc. of pyridine containing from methanol until pure- The dye sensmzed 1 cc. 01' triethylamine. The mixture was heated silver-bromoiodide emulsion to 530 m with a under reflux for 3 minutes. cooled, and the dye maximum 480 precipitated by the addition of 2 volumes of ether.

Erample XII The separated residue was washed several times 0,11. with water while allowing the tacky solid to gradl; ually solidify before filtering. The solid was then iL 11:0 purified by boiling out with several 5 cc. portions of methanol. The final residue was crystallized N 8 several times from methanol to obtain the pure l 4 dye. The dye sensitized a silver-bromoiodide one gram of 2. methy1mercapto 3 ethy1 hem emulsion to 730 m with a maximum at 680 my.

zothiazolium iodide and 0.25 gram or 2-amino-4- Example XV H 0 OH H 0 cm C am N- -N H|C 7 CH:

o=oH-oH=N- CH=CHOH=C 010.-

ethyl-5-methyl-1,3;4-thiadiazolium iodide were Six grams of 2-(p-anilidovinyl) -1-ethyl-3,3,5- dissolved in 10 cc. of pyridine containing 1 cc. of

triethylamine. The mixture was heated under reflux until the methyl mercaptan was dissi- Example XIII One gram oi Z-(p-anilidovinyl)-3-ethyl-6- methoxy benzoselenazolium iodide and 0.25 gram 7 of 2-amino-4-ethyl-5-methyl-1,3,4-thiadiazolium iodide were dissolved in 2 cc. of pyridine containing 0.1 cc. of acetic anhydride and 0.1 cc. of triethylamine. The mixture was heated under 'refiux for 1 minute. cooled, and diluted with water.

n.) ethylamine.

0 potassium perchlorate.

trimethyl indoleninium iodide and 2.5 grams of 2- amino-4- ethyl-5- methyl- 1,3,4,- thiadiazoiium iodide were dissolved in cc. of pyridine containing 2 cc. of acetic anhydride and 4 cc. of tri- The mixture was heated on a steam bath for 5 minutes, cooled, and the dye precipitated by the addition of several volumes of ether. The precipitate was dissolved in 50-75 cc. of methanol, and reprecipitated as the perchlorate salt by the addition of an aqueous solution of The crystals which separated out were filtered of! and recrystallized from ethyl alcohol. The dye sensitized a silverbromoiodide emulsion to 680 my. with a maximum at 620 inpi 11 Isample xv] (323: 5.0- s N---N l'bur grams of 2-(p-anllidovinyl) -3-methylthiamlinium iodide and 1.5 grams of 2-amino-4- ethyl-5-methyl-1,3,4-thiadiazolium iodide were dissolved in cc. of pyridine containing 1 cc. of acetic anhydride and 3 cc. of triethylamine. The mixture was gently heated on a steam bath for several minutes, cooled, and the dye precipitated by the addition of 2 volumeso! ether. The precipitate was dissolved in an adequate amount oi hot water and the oily impurities separated. The aqueous solution of the dye was precipitated as the perchlorate salt by the addition of an aqueous solution or potassium perchlorate. The perchlorate solution which separated out from the aqueous solution was filtered off and recrystallized from n-butanol. The dye sensitized a silver-bromoiodide emulsion to 650 m with a maximum at 800 m Example XVII 01H! anol. The dye sensitized a silver-bromoiodide emulsion to 720 m with a maximum at 690 m Example XVIII One gram of 2-(B-acetanilidovinyl)-3-ethy1- 4,5-benzo-benmxazolium iodide and 0.3 gram of 2-amino-4-ethy1 5 methyl-1,3,4-thiadiazolium iodide were dissolved in 5 cc. of pyridine containing 0.5 cc. of triethylamine and 0.5 cc. of acetic anhydride. The mixture was heated un der reflux for 3 minutes, after which time 1 cc. of triethylamine was added and the mixture heated for an additional 2 minutes. Upon cooling, the dye crystals were precipitated by adding 2 volumes of ether to the reaction mixture. The dye chrystals which separated out were filtered off and recrystallized from methanol. The dye sensitized a silver-bromoiodide emulsion to 660 m with a maximum at 630 m Example XIX CgHs o on,

p3OH=OH-OH=C 010is are Four grams of Z-(B-acetanilidovinyl)-3-ethyl- 5,6-dimethyl benzoxazolium iodide and 1.5 grams of 2-amino-4-ethyl-5-methyl-1,3,4-thiadiazolium iodide were dissolved in cc. of pyridine containing 2 cc. of triethylamine. The mixture was heated under reflux for 5 minutes, cooled, and diluted with 2-3 volumes of water. The dye which separated out was filtered ofl and re- OCH:

crystallized from methanol, redissolved in methanol and reprecipitated out as the perchlorate salt by the addition of an aqueous solution of potassium perchlorate. The perchlorate dye crystals were further purified by recrystallizing from methanol. The dye sensitized a silverbromoiodide emulsion to 680 m with a maximum at 630 mp.

Example XX One gram of 2-(fi-acetanilidovinyl)-3-ethyd-5- phenyl benzoxazolium iodide and 0.25 gram of 2 amino 4 ethyl-5-methyl-1,3,4-thiadiazolium iodide were dissolved in 12 cc. of pyridine containing 1 cc. of triethylamine and 0.5 cc. of acetic anhydride. The mixture was heated over a steam bath for 5 minutes, cooled, and diluted 8,500,118 13 14 with 8 volumes of water. The crystals which gram of z-amino-i-ethyl-o-methyl-1,3,4-thiaseparated out were filtered oil. and recrystallized wllum iodide. from methanol as the perchlorate salt. The dye Example XXIV 411B: nHl sensitized a silver-bromoiodide emulsion to 660 One gram of 2-[4l-acetanllido butadienyl-3- me. with a maximum at 610 eethyl-benzothiazolium iodide and 0.3 gram of 2- Example xx am1no-4-ethyl-5-methyl-1,3,4-thladiazolium io- 43,111 i l one gram fiv nyl thy1- dide were dissolved in 10 cc. of pyridine con- -m Y hehzoxa-lolium iodide d gram 0! taining 0.5 cc. of triethylamine. The mixture 2 amino Y 1 was heated under reflux for 3-5 minutes, cooled, iodide were dissolved in 10 cc. of pyridine conand diluted t 2 3 volumes of t The mining 1 of triethylamme i the solution crystals which separated out were filtered oil and agitated with a glass rod for mmutes at room recrystallized from propanol. The dye sensitized decanted and the residue washed with water 30 a maximum at 690 and then dissolved in cold methanol. One cc. of Example XXV 8 N El S o=oH-on=N-ti d-cn=cH-on=o I 1 0 (Elm aHs a 20% aqueous solution of sodium perchlorate Example IV was repeated with the exception was addedtothe filtered methanol solution. The that an equivalent amount of 1,4-diethyl-2- trinuclear dye precipitated as the perchlorate amino-S-methyl-1,3,4-triazoiium iodide was subsalt and was purified by recrystallizing from hot stituted for 2-amino-4-ethyl-5-methyl-1,3,4-thimethanol. The dye sensitized a silver-bromoadiazolium iodide. iod de s o to 550 m with a maximum at In the preparation 01 emulsions containing 560 m l. p these trinuclear cyanine dyes, the dye may be Example XXII dissolved in methyl or ethyl alcohol and the s N 31111 s e 1110-- OH:

c=cH-on=N-y d-oE=oH-oH=o I- (51E! (51E; One gram of 2-(B-acetanilidovinyl)-3-ethyl-5- alcoholic solution containing from 5 to millimethyl-benzothiazollum iodide and 0.3 gram of 5 grams oi. the dye added to a liter of emulsion. 2 amino 4-ethyl-5-methyl-1,3,4-thiadiazolium While in general practice it may not be necesiodide were dissolved in 10 cc. of pyridine consary to add the dye in the amounts larger than mining 1 0- Of triethylflmihei The mlXtule those above given, generally, for satisfactory rewas heated under reflux f0! 5 minutes, cooled sults, amounts ranging from 5 to 50 milligrams and diluted with several volumes of water. The are m i i; t obtain t maximum sensitizing cry a s which Separated were filtered Ofi effect. However, we do not wish to limit our nd recrystallized from methanol The dye invention to the quantities just indicated as the sensitized a silver-bromoiodide emulsion to 720 most suitable amount will, in each case, be found mu. withami-ximum at 690 i by a few comparative experiments. The dye Example XXIII may be added to the emulsion in form 0! solu- QflI i s N 1| /s H0O OH:

o=on-on=N-tt d-on-onon=o L o 61H; lHl

Example XXII was repeated with the exceptions. Suitable solvents as indicated in the extion that 0.3 gram of 2-amino-4-ethyl-5-methylamples are the alcohols, for instance, methyl or 1,3.4-oxadlazolium iodide was substituted for 0.3 ethyl alcohol which may be anhydrous or diluted 15 with a small volume of water. In actual practice. the dyes are applied to the emulsion during any stage of its production. However, they are preferably added to the finished emulsion before coating.

The diagrammatic spectrogram constituting 16 invention be defined only by the accompanying claims.

We claim: 1. A photographic gelatino silver-halide emulsion which contains a trinuclear cyanine dye characterized by the following general formula:

tain preferred embodiments of the invention, the same is not limited to the foregoing examples, illustrations or to the specific details given therein, but is capable of variations and modifications as to the reactants, proportions and conditions employed. Accordingly, it is intended that the wherein A is the residue of a heterocyclic nitrogenous compound, R represents a member selected from the class consisting of alkyl and aralkyl groups, X represents an anionic acid radical, Y represents a member selected from the class consisting of oxygen, sulfur, and NM, wherein R1 is a member selected from the class consisting of hydrogen and alkyl groups, m represents 0 a positive integer of from 1 to 3, and 9 represents a positive integer of from 1 to 2.

2. A photographic gelatino silver-halide emulsion which contains a trinuclear cyanine dye characterized by the following formula:

3. A photographic gelatino silver-halide emulsion which contains a trinuclear cyanine dye characterized by the following formula:

4. A photographic gelatino silver-halide emulsion which contains a trinuclear cyanine dye characterized by the following formula: I

ALFRED W. ANISH. CHARLES A. CLARK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,166,736 White et al July 18, 1939 2,263,018 Sprague Nov. 18, 1941 2,355,654 Kendall et al Aug. 15, 1944 

1. A PHOTOGRAPHIC GELATINO SILVER-HALIDE EMULSION WHICH CONTAINS A TRINUCLEAR CYANINE DYE CHARACTERIZED BY THE FOLLOWING GENERAL FORMULA: 